That is what I say to seatmates on planes and trains. I don't use my voice, though. I express a preference for solitude by hiding my face in a book or wearing earbuds. A bitchy resting face also helps me communicate—without ever having to talk—that I don't want to say anything to you, stranger. Pretend I'm not here. But the person in the adjacent seat doesn't always receive the message.

Social cues that speak so loudly to some simply fly over the heads of others. And so it's inevitable that, as a person who travels, you will encounter a frightening "new friend" who comes on too strong when you're desperate to stare out the window during your flight and quietly contemplate dinner options.

You'll have to handle the situation with grace, like the respectful adult that you are, or be stuck in a confined space for many hours with the random, possibly unstable person that you've offended. You can become a martyr, sacrifice yourself to the god of inane small talk, and engage. Or you can be very mean and deflect conversation by coming across as a terrible person.

But there's another way—a peaceable middle ground. I asked Jay Remer, an etiquette consultant based in St. Andrews, New Brunswick, who is known as Canada's "Etiquette Guy," for advice on how to cope when one's airplane seatmate insists on chatting, having no cognizance of annoyed facial expressions and attempts to feign sleep. First, Remer told me that both parties need to "take responsibility for this interaction." It is disrespectful, said Remer, to dance around the issue because you're afraid of what will happen.

You knew this was coming, guys. The appropriate course of action is direct communication.

"People need to have enough self-confidence in themselves to be able to say how they feel about something without self-doubt," said Remer. "If someone is bugging you, say, 'I just want some time to myself.' [If you] give a reason why, make sure it has nothing to do with the other person. Because we're human beings, we tend to take things personally every chance we get."

Don't want to give a reason for your antisocial ways? You don't have to. According to Remer, "You should never have to give an explanation. If I didn't want to connect, I would say, 'You know what, I just need to have some time. I just cannot get into a conversation right now. Thank you for wanting to connect with me, but I have so much on my mind right now, I need a few minutes to collect my thoughts.' That'll do it."

That'll do it because your seatmate probably isn't Ted Bundy. He's just lonely. Or very outgoing. Either way, you need to have the talk if you want to squelch his hopeful banter.